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Integrated seat-post clamp in the seat cluster/top tube

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Integrated seat-post clamp in the seat cluster/top tube

Old 01-08-13, 11:45 AM
  #1  
Tychom
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Integrated seat-post clamp in the seat cluster/top tube

So I'm not really sure where else in the forums to post this but it seems somewhat relevant. I saw this today (on something to maybe buy..) and I'm just thinking it looks like a rather bad and dangerous idea, on the other hand it's from a rather reputable french frame builder, Alain Michel, who whilst he's made a number of interesting frames none have been considered dangerous.

What it is is a seatpost clamp integrated into the top tube of the frame using a hidden bolt and clamp similar to on certain Cinelli stems (those Cinelli stems that had this particular setup often didnt work so well, for what it's worth):



Looks a little mad to me and surely prone to cracking as it's removing a lot of material from the tube (it looks like it avoids the lug, just) at a place of high stress on the frame.

Anybody any thoughts on it, could there be any positives to this?
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Old 01-08-13, 12:01 PM
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unterhausen
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I know someone that used to build with a set of ears inside the tube, but stopped because it's a bad idea. The wedge idea is worse, IMO. The only reason people do it is for looks. I don't think that's a particularly high stress area. On mountain bikes with long seat posts it can be a problem on the top of the seat tube/top tube joint, but I've never seen a horizontal top tube bike have issues in the top tube.
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Old 01-08-13, 11:42 PM
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fietsbob
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I'm just thinking it looks like a rather bad and dangerous idea
then walk away..

i got one of those cinelli 1R stems , I'm using a 0.4mm undersize Nitto 26.0handle bar in it .
20 years its been OK.. but Im a old slow guy now , never a hard rider..
got 2, one I bored a cable hanger hole thru for cantilevers..
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Old 01-11-13, 12:05 PM
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ksisler
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Originally Posted by Tychom View Post
So I'm not really sure where else in the forums to post this but it seems somewhat relevant. I saw this today (on something to maybe buy..) and I'm just thinking it looks like a rather bad and dangerous idea, on the other hand it's from a rather reputable french frame builder, Alain Michel, who whilst he's made a number of interesting frames none have been considered dangerous.

What it is is a seatpost clamp integrated into the top tube of the frame using a hidden bolt and clamp similar to on certain Cinelli stems (those Cinelli stems that had this particular setup often didnt work so well, for what it's worth): Looks a little mad to me and surely prone to cracking as it's removing a lot of material from the tube (it looks like it avoids the lug, just) at a place of high stress on the frame. Anybody any thoughts on it, could there be any positives to this?
OP; Looks like it is just different to be different rather than for any viable reason. Given that there are serveral/many good ways to do a SP clamp, I wouldn't do or buy a potentially sketchy one.
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Old 01-11-13, 01:23 PM
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unterhausen
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Originally Posted by fietsbob View Post
i got one of those cinelli 1R stems , I'm using a 0.4mm undersize Nitto 26.0handle bar in it .
20 years its been OK.. but Im a old slow guy now , never a hard rider..
The one on my main road bike was great for almost 30 years. Then one day, boom, handlebars free to rotate. Fortunately I still had steering and rode it out. Actually rode 2 miles home. Holding the bars at the neutral axis of rotation. Even before that I could never stop that stem from creaking.
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Old 01-17-13, 03:47 PM
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For posterity sake here's another photo of that clamp -



Yeah, I figured I'd pick it up - my size, a little different and a nice price. Seems to clamp ok, I guess we'll see how well that lasts.

Some other shots of the frame as a whole for anyone curious -





Not great photos, i'll have better in the correct forums at some point. But the interesting parts - the center sections of the down tube and seat tube are tear drop shaped (not simply flattened), as are sections of the seat stays and the fork. Also the seat tube is crimped to aid removal of the rear wheel. No idea what the tubing is, but it's a bit different.
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Old 01-17-13, 05:44 PM
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thanks for the pictures, that's a nice bike. My track frame has 2 seat post bolts -- builder really, really didn't want that seatpost to slip. Don't know if I ever knew who built it, but I certainly don't know now.
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Old 01-17-13, 05:55 PM
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That is an interesting bike. A lot depends on the engineering and execution on the seat post clamp. There is a ratio, not unlike a gear ratio that exists in such a mechanism. If it was done right and you use a post that can take the force and apply the right amount of torque it can work fine but it is an added level of unnecessary complication. So much is dependent on the skill of the designer and fabricator with a design like this.

I like forming tubes myself for the (tig welded) frames I sell. However, I am not partial to shaped tubes in lugged frames.
My interest in this bike would be in the builder and his history of his work. I have a frame built by an innovative Parisian builder, Giuseppe Limongi in '74 or so and consider it one of my valued possessions but I am pretty sure no one else cares.

If the price is reasonable I would consider it for my collection. I would not buy it as my main bike.
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Old 01-17-13, 06:26 PM
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RE Cinnelli 1R,
Even before that I could never stop that stem from creaking.
a little Red Loctite worked for Me..

but I mostly climbed without much Upper body workout pulling on the handlebars..
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Old 01-18-13, 03:00 PM
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It might have been an early track frame... from the ST crimp, the close tire clearances front and rear and the minimal clearance between the front tire and the DT... perhaps it is from a era just before the wild and crazy stuff started to appear in the racing frame world.
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Old 06-11-13, 08:31 PM
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Internal workings of clamp

I've been searching high and low for something like this. Do you you still have that bike? Could you take a pic of the internal guts that make it work? This would be most appreciated.

I'd love to get a better understanding on how the wedge system works in there.
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